storage: add MVCCIterKind type

It will be used in a subsequent PR.

Release note: None

pkg/storage/engine.go

@@ -214,6 +214,20 @@ type IterOptions struct {
  MinTimestampHint, MaxTimestampHint hlc.Timestamp
 }
 
+// MVCCIterKind is used to inform Reader about the kind of iteration desired
+// by the caller.
+type MVCCIterKind int
+
+const (
+ // Intents appear interleaved with keys, even if they are in a separated
+ // lock table.
+ MVCCKeyAndIntentsIterKind MVCCIterKind = iota
+ // Separated intents will not be seen. Any interleaved intents may be
+ // seen, but no correctness properties are derivable from such partial
+ // knowledge of intents.
+ MVCCKeyIterKind
+)
+
 // Reader is the read interface to an engine's data.
 type Reader interface {
  // Close closes the reader, freeing up any outstanding resources. Note that
@@ -269,10 +283,12 @@ type Reader interface {
  // error. Note that this method is not expected take into account the
  // timestamp of the end key; all MVCCKeys at end.Key are considered excluded
  // in the iteration.
+ // TODO(sumeer): add MVCCIterKind parameter.
  MVCCIterate(start, end roachpb.Key, f func(MVCCKeyValue) error) error
  // NewIterator returns a new instance of an MVCCIterator over this
  // engine. The caller must invoke MVCCIterator.Close() when finished
  // with the iterator to free resources.
+ // TODO(sumeer): add MVCCIterKind parameter and rename to NewMVCCIterator.
  NewIterator(opts IterOptions) MVCCIterator
 }